Shingled roofs utilize individual, overlapping units of prepared roofing materials referred to as shingles. Roofing shingles most commonly are made out of asphalt or wood, such as cut or split cedar and redwood. They also may be fabricated from stone, fiber cement, metal, and plastic. Shingled roofs utilize various flashing and other components where the fields of a roof terminate or intersect, such as the eaves, gables, valleys, ridges, and hips of a roof. Even in roofs having many different intersecting or overlapping fields, however, the basic construction of shingled roofs across the major expanse of a roof is fairly standard.
Most commonly, the roof substructure includes rafters. The rafters typically are dimensional wood boards which run vertically, i.e., along the pitch of the roof from the eaves to the ridges. Sheathing is installed on the rafters to provide a deck. The deck provides the structural support for the roof cover. The sheathing typically is plywood, oriented, strand board (OSB), or wooden planks. Spaced boards also may be used to provide a deck.
An underlayment, usually consisting of asphalt-saturated felt (tar paper), is generally installed to protect the deck. Other barrier webs may be installed both above and below the deck, such as reflective barriers or moisture barriers. Ice and water barriers often will be installed along the eaves and valleys of the roof.
The shingles provide the cover for the roof. For example, so-called strip or 3-tab asphalt shingles are in widespread use. They are have a somewhat elongated, rectangular shape. A pair of cutouts run partially across the shingle from its lower or butt edge to define the three tabs. The shingles may incorporate a factory-applied strip or spots of heat sensitive adhesive on their upper, lap portions. A starter strip also typically will be installed along the eaves to cover portions of the deck that otherwise would be exposed by the cutouts in the shingles.
The shingles are installed on the deck in overlapping rows or “courses” that run horizontally, i.e., across the pitch of the roof. The shingles are installed with their longer ends parallel to the eave. The first course is installed along the eave of the roof, typically over a starter strip. Successive courses are then laid up the slope of the roof. Typically, the shingles are installed without overlaps as they run along a course, but may be provided with Dutch laps at their ends. If the shingles are not self-sealing, adhesive may be applied to the upper, lap portion of the shingles as successive courses are installed. Overlapping courses of shingles will be more resistant to uplift in heavy wind if they are adhered to underlying course.
Overlapping courses are installed such that the butt edge of the course overlaps slightly more than half the width of the lower, underlying course of shingles. It will be appreciated that this installation pattern creates a head lap. That is, the pattern provides area of triple coverage: areas where the upper edge, mid portion, and butt edge of three courses overlap.
Roofs in general are designed to endure. Three-tab asphalt shingle roofs, for example, on average last 15 to 18 years. Eventually, however, they will deteriorate to the point where the cover is no longer weather proof. Removing and replacing the shingles has a number of advantages, especially where the roof is in serious disrepair. Stripping the old shingles will expose the roof deck and allow repair of any deteriorated underlayment and sheathing. Removing the old shingles also minimizes the load on the roof substructure.
On the other hand, removing an existing roof can be expensive and can disrupt occupants of a building. It also creates large quantities of waste that must be disposed of, and eliminates not only the existing roof, but whatever insulation value the existing roof may have provided. It also is quicker and cheaper to simply install new shingles over the existing shingles.
For example, new courses may be nested into existing courses by butting the top edge of the new shingles against the butt edge of the old shingles. Tapered wood filler strips or “feathering” strips also may be used, especially with thicker shingles. The feathering strips will be placed along the butt edge of the old shingles to create a level surface for installing new shingles. Recovering existing shingles with new shingles, however, greatly increase the load on the roof substructure.
Metal panel covers also have been used to “recover” deteriorated shingle roofs. A new metal cover, or “recover” over an existing cover will add much less weight to the roof as compared to simply installing new shingles over the old. Metal panel recovers also offer significantly longer service life—up to 40 years or more. That extended service life, however, often comes with a much greater cost. Metal panel recovers can be at a significant disadvantage relative to cheaper alternatives such as simply re-shingling the roof.
Metal panel covers, whether a new installation or a recover, utilize rather elongated metal panels installed along the slope of a roof. Each cover panel is typically about a foot to three feet in width. Though they may be cut to any length, they commonly are 30 to 40 feet long and may run as long as 200 feet. The lateral edges of the panels are bent in various configurations to form upwardly extending sides and a trough in the middle. The trough is where most of the water will be shed from the roof.
Adjacent panels are joined along their upwardly extending sides to create relatively narrow seams which are elevated above the trough. The panels are laid out such that the seams run vertically, i.e., with the slope of the roof. The panels also may have one or more ridges running vertically through the trough, and it is those vertically oriented seams and ridges that create the distinctive appearance that consumers associate with metal roofs. More importantly, however, since the seams between adjacent panels are formed a few inches above the troughs where most rain will be shed, metal panel roofs can be very resistant to leaking.
Raised-seam, metal panels may be classified according to the manner in which they are installed. So called “through panel” or “exposed” fastener panels are installed with screws or other fasteners that penetrate through the cover panels. The panels typically are laid over a roof so that their sides overlap and form a raised, often trapezoidal shaped seam or “lap” rib. The panels then are joined together along the lap rib by, e.g., gasketed screws. Gasketed screws also are driven through the trough. When used to recover a shingled roof, the through-panel fasters will be driven in the shingles and sheathing. Leakage around the fastener, at least initially, is not a significant problem. Over time, however, the elastomeric material from which the screw gaskets are fabricated can deteriorate, and leaks tend to develop around penetrating fasteners.
“Standing seam” covers can provide better resistance to leakage over longer periods of time and, in the eyes of many beholders, provide a more beautiful roof. In a standing seam cover, the metal panels are secured with concealed clips instead of unsightly and leak-prone penetrating fasteners. Most commonly, a plurality of relatively small panel clips are installed in a fairly widely spaced, array running vertically (along the slope of the roof) in what will become a seam line between adjacent panels. Panels are then installed between the vertical lines of clips, with the upturned seam edges of the panels abutting and mating with the clips and each other. There are no penetrations through the panels when clips are used. Moreover, all gaps between the panels and the clips are elevated well above the trough through which most water runoff occurs. Thus, standing seam panel covers provide better, longer resistance to leakage as compared to covers using screws or other “through panel” fasteners that penetrate the panels.
There are many conventional systems that use non-penetrating clips with standing seam metal panels for new installations. In new installations, the clips typically are mounted to an array of spaced, elongated support members or “purlins” which are mounted across the structural rafters of a roof substructure. The purlins run horizontally across the rafters, i.e., across the slope of the roof.
Such systems are disclosed in U.S. Pat. No. 4,575,983 to H. Lott, Jr. et al. Panel clips are mounted on purlins, and the metal panels secured to the clips. The panels disclosed therein are asymmetrical standing seam panels. Asymmetrical panels have mating male-female connections, each panel having a male connection formed in one side and a female connection formed in its other side. Thus, installation must proceed in a certain direction across the roof, and removal for repair must proceed in the opposite direction.
Symmetrical standing seam panels, however, have sides which are identical and are joined with a separate seam cover. Symmetrical panels, therefore, may be installed in either direction. A damaged panel also may be removed for replacement without removing any adjacent panels. Examples of new installation, symmetrical standing seam roof covers where non-penetrating individual clips are mounted on purlins are disclosed in U.S. Pat. No. 4,649,684 to L. Petree et al. Other covers, such as those disclosed in U.S. Pat. No. 6,354,045 to M Boone et al. and U.S. Pat. No. 5,737,892 to P. Greenberg, utilize individual and elongated, “continuous” clips that are mounted to and span adjacent purlins. While they are more costly than covers using asymmetrical panels, such symmetrical panel covers can offer improved leak protection, better uplift resistance, and longer service life.
U.S. Pat. No. 8,887,464 to C. Smith and U.S. Pat. No. 8,938,924 to C. Smith disclose standing seam metal panel recovers for installation over existing metal panel roofs. Those systems include systems where the panels are installed using a combination of individual and continuous clips. The individual clips are arranged in linear arrays, each individual clip being mounted on a single purlin. Thus, the base of the clip has a very limited span, typically only a few inches, just long enough to run across the width of the purlin with some play. The continuous clips are extremely elongated—up to 30 feet long—with each continuous clip spanning at least two, or more typically, many purlins.
The upper surface of a shingled roof, however, is by its nature quite uneven. It is unsuited for use with individual clips such as those disclosed in the '464 and '924 patents. Moreover, extremely long continuous clips are difficult to work with during installation. Thus, when metal panels have been used to recover deteriorated shingled roofs, various supporting structures have been provided to provide a more even surface upon which the metal panels may be installed.
For example, a new underlayment may be laid over the existing shingles and new, exposed fastener metal panels installed over the underlayment. Alternately, wood boards or “battens” may be nailed into the existing deck and running horizontally across the existing shingles. Exposed fastener panels then may be installed on the battens. See Tri County Metals, Can You Install Metal Roofing Over Shingles? (http://tricountymetals.com/can-you-install-metal-roofing-over-shingles/); and D. Chasar, Metal Roof Retrofit on a Hurricane Damaged Home (Copyright 2014 Florida Solar Energy Center) (http://www.ba-pirc.org/CASESTUD/hdh_roof/index.htm).
Alternatively, wood batten and counter-batten systems have been used to provide a supporting structure upon which metal panels may be installed. Such systems are disclosed, for example, in Houston Cool Metal Roofs, The Texas Smart Roof™: The Coolest Roof in Texas (http://www.houstoncoolmetalroofs.com/cool-roof-information/cool-roof-design-texas/). Similar metal batten-counter-batten systems have been devised for installation of metal tiles and shingles. Cool Roof Canada, Radiant Ventilated Cool Roofing: Metal ‘ASV’ Batten Ventilation System for Stone Coated Steel Roofing (http://www.coolroofcanada.com/cool-roof-batten.html).
Such systems employ horizontally oriented battens and vertically oriented “cross-battens.” That crisscrossing pattern not only elevates the recover well above the existing shingles, it allows for above sheathing ventilation (ASV). That is, convective air currents caused by the heating of the roof have a path allowing flow of heated air from the eave toward the ridge.
Above sheathing ventilation can dramatically reduce the amount of heat transmitted through the roof into a structure. It will be appreciated, however, that convective flow paths created by batten-counter-batten systems are somewhat tortuous. In addition, and while metal systems are lighter weight than wood and are said to be less expensive, batten-counter-batten systems typically will add both cost and weight to a recover system.
The statements in this section are intended to provide background information related to the invention disclosed and claimed herein. Such information may or may not constitute prior art. It will be appreciated from the foregoing, however, that there remains a need for new and improved systems, apparatus and methods for installing metal panels over existing shingled roofs. Such disadvantages and others inherent in the prior art are addressed by various aspects and embodiments of the subject invention.